The invention pertains to an orbital shaker.
During the operation of orbitally shaken bioreactors, imbalance-caused forces and moments develop in use, which depend on the variable loading of the shaker table (mass and geometry of the containers, properties of the contents, and also the mass and location of the center of gravity of the shaker table), on the shaking diameter, and on the shaking frequency, among other factors. These imbalances lead to undesirable vibrations of the orbital shaker, to increased wear, to noise pollution, and to deviations from the defined shaking path. As a result, these effects limit the maximum possible shaking frequency for a given load and a given shaking diameter. For some bioengineering processes, however, high shaking frequencies are necessary to ensure that the cultures are supplied with enough oxygen and that sufficient mixing is achieved.
To keep the exciting imbalance forces and moments as low as possible, balancing weights can be attached to orbital shakers. But because both the loading of the shaker table (in particular the mass of the table and the location of its center of gravity) and the shaking diameter often change, rebalancing is required every time one of these parameters is changed.
Orbital shakers commercially available today usually do not offer any possibility of adapting the balancing state to the variable loading.
Only a few manufacturers offer the possibility of manually adjusting compensating weights to balance the system.
U.S. Pat. No. 8,226,291 B2 discloses an orbital shaker with a balancing device, in which the angle between two compensating masses arranged symmetrically in a balancing plane underneath the shaker table can be manually adjusted, so that the resulting radial centrifugal force can be varied.
In the shakers available on the market, it is not possible to vary the adjustment of the compensating masses in a continuously variable manner. It is impossible to fine-tune the balancing device, and the maximum possible rotational speeds are therefore limited. To carry out the manual balancing disclosed in U.S. Pat. No. 8,226,291, it is necessary to partially disassemble the orbital shaker, which demands a certain amount of technical know-how. In addition, this adjusting work takes time. The disadvantages of the prior art have the result that the manual adjustment of the compensating masses is not carried out in practice every time there is change in the load or in the shaking diameter. The maximum possible shaking frequencies are therefore severely limited. This limitation of the maximum shaking frequency has a negative influence on some bioengineering processes. In addition, the vibrations lead to considerable wear and to increased noise pollution.
U.S. Pat. No. 8,226,291 B2 also discloses an automatic positioning of the compensating masses in a balancing plane by means of a servomotor. To control the position of the compensating masses automatically, sensors and a control unit are required. This is therefore an active system with automatic positioning of the compensating masses.
The active automatic balancing described in U.S. Pat. No. 8,226,291 B2 is associated with high acquisition costs and the danger of the failure of the required sensors, of the actuating mechanisms, and/or of the electronic circuitry. The failure of an orbital shaker is usually associated with the loss of the shaken culture. Depending on the experiment, the failure of an orbital shaker in a research laboratory can lead to the loss of several weeks of work. This results in direct costs for personnel and the use of the laboratory. Consequential costs can arise through delays in the market introduction of the product being investigated. If an orbital shaker fails during production, considerable downtime costs are incurred as a result of the loss of product.
The adjusting of the compensating masses described in U.S. Pat. No. 8,226,291 B2 can compensate only for the imbalance force. There is no additional ability to compensate for the imbalance moment attributable to the vertical distance between the balancing plane and the center of gravity of the load.
U.S. Pat. No. 5,558,437 discloses a dynamic compensation of the imbalance force and of the imbalance moment. Two balancing planes are provided underneath the shaker table. In the upper balancing plane, the compensating weight is located on the opposite side of the joint linkage to the shaker table, this linkage being arranged eccentrically to the rotational axis of the rotor. In the lower balancing plane, the compensating weight is located on the same side as the joint linkage to the shaker table, the linkage again being arranged eccentrically to the rotational axis of the rotor. By tuning the parameters (radial distance, mass of the weights and vertical distance), the system can be balanced in such a way that the imbalance force and the imbalance moment are compensated. No provisions are made for a manual or automatic adjustment of the parameters nor for an adaptation to the variable loading of the shaker table.